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Recovery of neural function in lobsters following sub-lethal Salmosan® exposure

Description

The Canadian aquaculture industry is currently valued at $1 billion per year, most of which is generated through salmon farming along Canada’s Pacific and Atlantic Coasts. Rearing salmon in sea cages can pose many challenges to farmers, including the need to treat for sea lice infestations in order to maintain healthy farmed populations and for minimizing any risk of sea lice transfer to wild fish. As with terrestrial farming, the salmon aquaculture industry relies on drugs and pesticides, collectively known as ‘therapeutants’, to control parasites. These products are regulated by Health Canada under the Pest Control Products Act and its regulations to protect human health and the environment. Salmosan® is one of only three therapeutants currently approved by Health Canada (under Emergency Registration) for the treatment of sea lice on farmed salmon in Atlantic Canada. At certain concentrations, Salmosan® causes continuous and potentially lethal muscle stimulation in sea lice and other crustaceans but recovery from non-lethal exposure has been observed in previous studies. Salmosan® is mixed in seawater at prescribed concentrations for the treatment of sea lice in well boats or in salmon pens using a tarp method and is released post-treatment to disperse into the surrounding water. Potential impacts to non-target species depends on the distance that any remaining pesticide travels before becoming too diluted to have a biological effect. Sublethal effects observed in the laboratory, such as temporary paralysis in lobsters under specific exposure conditions, could leave them vulnerable to predation and other environmental stressors.

Fisheries and Oceans Canada (DFO) is responsible for ensuring that all aquaculture-related activities are safe for wild fish and their habitats. Historically, Salmosan® research by DFO focused on acute lethality to lobsters given their importance to Atlantic fisheries. While it is important to identify lethal doses, information is needed on sub-lethal effects of exposure in order to model, predict, and better manage environmental impacts when therapeutants are used for sea lice treatment.

The objective of this research is to determine the rate at which lobster activity, behaviour and affected enzymatic activity return to normal levels following sub-lethal treatments that mimic actual industry usage of Salmosan®. This information is needed by DFO in order to better predict what impact, if any, currently prescribed sea lice treatment using Salmosan® has on lobsters; to inform the development of monitoring guidelines; and to identify opportunities for improved treatment protocols to maximize their efficiency for sea lice management without affecting lobster fisheries.

Program Name

National Contaminants Advisory Group (NCAG)

Year(s)

2015 - 2017

Ecoregion(s)

Pacific: North Coast and Hecate Strait

Principal Investigator(s)

Tillmann Benfey
Professor of Biology, University of New Brunswick

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